The invention concerns an injection-molding unit for an injection-molding machine to process compounds that can be plasticized such as plastics, ceramic compounds or other powdered compounds.
This type of injection-molding unit is known from EP 0 752 303 A1, which uses an electromechanical injection-molding unit to inject the plasticizable compound into the hollow space of a mold clamped into a mold-closing unit and an electromechanical rotary motor to turn a conveyor. The injection unit sits on a support, which is connected to a carrier block via cross beams. These cross beams are used to guide an injection bridge. The conveyor and the ball roll spindle of the injection-molding unit are coaxial to one another. The rotary motor and the injection motor are both arranged on the injection bridge and move with it. They transmit their drive torque to drive elements arranged coaxial to one another and coaxial to the spray axis. Both conveyor worms and ball roll spindles are rotary-mounted on the injection bridge. That way, no radial forces are transmitted from the injection bridge to the cross beams, which is essential to detect the reaction forces there, but this involves considerable expense for rotary mounting the conveyor and the spindle. Since the bearings are not in a housing, it is difficult to protect them from getting dirty. Since the force needed to move the injection bridge axially is transmitted by tapering the spindle, bearing and spindle sheath back to the worm, many different components must be assembled at some expense, so this unit cannot be made in a modular design. The mounting is done so that the bearings that absorb the relatively high forces during the axial movement of the worm, are inside, while the bearings that absorb the comparatively lower dosing forces are outside. This arrangement of the bearings basically parallel to one another is a disadvantage.
It is also known from DE 43 44 335 A1 how to arrange electromechanical drives to make the worm rotate and make the worm move axially with their axes flush with the axis of the worm. To make this possible, at least one of the motors must be a hollow shaft motor, so that despite its compact design, it is expensive.
Starting from this state of the art, the problem of this invention is to create a simple, compact coupling of the drive elements for dosing and injecting on an injection-molding unit.
This problem is solved by the features of the injection-molding unit of the present invention.
Compared to the known embodiments, the rotating mountings are now no longer mounted separately by themselves, but are now mounted axially between the two drive elements, which makes it possible for the axial forces to be transmitted directly. This saves one bearing element, on one hand; and on the other hand, the local proximity gained thereby creates the structural conditions for the drive element to be arranged in a housing (claim 4), since that element effectively protects it from outside influences. However, it also creates the conditions so that a largely modular design with many structurally equal parts is possible. Arranging the axial bearing element directly between the first drive element and the other one makes a space-saving design possible, on one hand, and, on the other hand, where high axial forces occur during the axial movement of the worm, larger bearings can be provided, while smaller bearings can be used for the dosing forces. This is more compatible with the forces that actually occur than is usual in the state of the art.
Although the same parts are also arranged largely symmetrically to the spraying axis to make the load on the injection-molding unit symmetrical, in the design in claims 7 to 10, the forces are effectively reduced by assigning a planet gear to the means of linear movement. To protect this drive from outside influences, it can be surrounded by a pipe so that it looks like a piston/cylinder unit on the outside. BRIEF DESCRIPTION OF THE FIGURES
The invention will be explained in greater detail below using the figures.
FIG. 1 shows a side view of an injection-molding unit supported on a machine base and set next to a mold in side view,
FIG. 2 shows an enlarged section along Line 2xe2x80x942 in FIG. 3,
FIG. 3 shows an enlarged section along line 3xe2x80x943 in FIG. 1,
FIG. 4 shows an angled section along line 4xe2x80x944 in FIG. 3,
FIG. 5 shows the view in FIG. 2 in another embodiment.